The present invention relates to endoscopic biopsy forceps that is passed through the forceps channel in an endoscope to collect a tissue specimen for biopsy from within a body cavity.
Endoscopic biopsy forceps generally comprises two integral assemblies of forceps cups and drive levers. The two integral assemblies of forceps cups and drive levers are provided at the distal end of a sheath. A manipulating wire extending through the sheath is moved back and forth along the longitudinal axis so that the drive levers pivot about a support shaft and the forceps cups are driven to open and close like beaks.
FIG. 16 shows a typical coupling structure for the drive lever and the manipulating wire in endoscopic biopsy forceps of this type. The distal end of a manipulating wire (not shown) is connected to a link plate 13 arranged parallel to a drive lever 8 and interposed between the manipulating wire and the drive lever. The link plate 13 is rotatably connected to the drive leber 8 by a rivet 18. Shown by 7 in FIG. 16 is a forceps cup.
Since the drive lever 8 and the link plate 13 are connected together in a xe2x80x9ccantileverxe2x80x9d manner by the rivet 18, wear, rattles and other phenomenon that occur during use may often cause them to come out of the parallel state as shown in FIG. 17. Consequently, the rivet 18 either skews or otherwise deforms to prevent smooth movement of the driver lever 8 and the link plate 13. In the worst case, the rivet 18 may come off.
The integral assembly of forceps cups and drive levers has heretofore been formed by cutting stainless bars and the like. However, in view of its extremely high cost, the assembly is currently formed by subjecting a plate material to press working (see Unexamined Published Japanese Patent Application (kokai) Nos. 276285/1997 and 24045/1998).
FIG. 18 shows an example of an integral assembly of a forceps cup 7 and a driver lever 8, which is produced by press working. FIG. 19 is a sectional view of the boundary 9 between the forceps cup 7 and the drive lever 8. As shown in FIGS. 18 and 19, the drive lever 8 and the boundary 9 are formed by bending a metal plate material so that one half of the plate material is closely contacted with the other half of the plate material
When a pair of forceps cups 7 are allowed to bite a mucosal membrane tissue of a living body, a large force acts on the forceps cups 7 in random directions and the concentrated stress works on the boundary 9 which is the neck of each forceps cup 7.
Since the boundary 9 which is formed by bending the metal plate material so that one half of the plate material is closely contacted with the other half of the plate material is vulnerable to lateral bending forces and, hence, the boundary 9 bends laterally in the direction indicated by arrow A in FIG. 18, often causing the forceps 7 to deform as if they have swiveled laterally.
An object, therefore, of the present invention is to provide endoscopic biopsy forceps that allow for smooth action of the drive levers to ensure that the forceps cups formed integral with them will positively open and close.
Endoscopic biopsy forceps according to a first aspect of the present invention comprises a sheath, two integral assemblies of forceps cups and drive levers that are provided at a distal end of the sheath and a manipulating wire extending through the sheath which is moved back and forth along a longitudinal axis so that the drive levers pivot about a support shaft and the forceps cups are driven to open and close like beaks. Parallel grooves are formed respectively in the drive levers in a direction perpendicular to a longitudinal axis of the support shaft. Connecting members for coupling the manipulating wire and the drive levers are coupled to the drive levers within the parallel grooves.
Preferably, each of the drive levers retains the two ends of an associated pin-shaped member extending across the parallel groove in a vertical direction, and the connecting members are plate-shaped link members each coupled pivotally to the respective pin-shaped member. Alternatively, the connecting members may be wire-shaped members each coupled pivotally to the respective pin-shaped member.
In another preferred embodiment, a through-hole is pierced in that part of the wall of each of the drive levers which faces the parallel groove, the connecting members are wire-shaped members extending through the respective through-holes, and a removal preventive member too large to pass through the through-hole is engaged with the distal end portion of each of the wire-shaped members. Alternatively, the wire-shaped members may each be formed of the distal end portion of the manipulating wire.
If desired, the forceps cups and the drive levers maybe formed of a plate material by press working. The drive levers may be formed in a generally U-shaped cross section.
Endoscopic biopsy forceps according to a second aspect of the present invention comprises a sheath, two integral assemblies of forceps cups and drive levers that are provided at a distal end of the sheath and a manipulating wire extending through the sheath which is moved back and forth along a longitudinal axis so that the drive levers pivot about a support shaft and the forceps cups are driven to open and close like beaks. A wire-shaped member provided at the tip of the manipulating wire is bent back to form a loop, and the material of which the drive levers are made forms a wire engaging portion at the distal end of each drive lever so that the loops of the wire-shaped member are brought into rotatable engagement with the wire engaging portions of the drive levers.
If desired, the forceps cups and the drive levers may be formed of a plate by press working, and the distal end portion of each wire engaging portion may be formed in a cylindrical round shape that centers on a longitudinal axis parallel to the support shaft and which is loosely fitted into the associated wire loop.
The wire engaging portions may be formed in such a way that the material of which the drive levers are formed is partially superposed on itself. Alternatively, the wire-shaped member may be formed of the distal end portion of the manipulating wire itself.
Another object of the invention is to provide durable endoscopic biopsy forceps that can be manufactured at low cost by forming integral assemblies of forceps cuss and drive levers by press working and which yet is resistant to lateral bending and subsequent deformation in the boundary between each forceps cups and the associated drive lever.
Endoscopic biopsy forceps according to a third aspect of the present invention comprises a sheath, two integral assemblies of forceps cups and drive levers that are formed by press working and which are provided at the distal end of the sheath and a manipulating wire extending through the sheath which is moved back and forth along a longitudinal axis so that the drive levers pivot about a support shaft and the forceps cups are driven to open and close like beaks. The boundary between each forceps cup and the associated drive lever is formed in a generally U-shaped cross section.
If desired, a hole through which the support shaft is passed is formed near the boundary between each forceps cup and the associated drive lever. Each drive lever may be formed as a part continuous to the boundary which has a generally U-shaped cross section.
The present disclosure relates to the subject matter contained in Japanese patent application Nos. Hei. 11-250068 (filed on Sep. 3, 1999), 11-253931 (filed on Sep. 8, 1999) and 11-255146 (filed on Sep. 9, 1999)), which are expressly incorporated herein by reference in their entireties.